Need help pricing cards

Hey so I have been collecting cards for a bit now and have never really wanted to sell but money is tight. I have a OP09-004 Shanks Wanted bounty card and I am confused on how to price this kind of stuff properly. I was offered $150 but I see higher prices on TCGplayer but are those listings as accurate as I can get or are there other sites/methods that can make this easier? I know this might break one of the rules of this subreddit but I’m really lost on how to do this kinda of stuff.